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The light clock: Error and implications


The light clock (a photon undergoing successive reflections between two particle mirrors a fixed distance apart) has commonly been used as a theoretical confirmation of the special-relativistic slowing of clock rates. In order to obtain that result one must describe the clock photon in a system moving relatively to the clock. However, contradictory frequency transformations for the photon, as observed from the mirrors, are then predicted by relatively moving observers. A correct and consistent analysis utilizes the Lorentz-invariant relative velocity and distance between the mirrors. An invariant time period is also then involved; a parallel is drawn between it and the invariance of cosmic time for internal processes in distant systems. Considering that space-time and momentum-energy are described by conjugate 4-vectors, it is conjectured that a time transformation occurs only in association with a transformation of energy.

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Schlegel, R. The light clock: Error and implications. Found Phys 10, 345–351 (1980).

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  • Reflection
  • Relative Velocity
  • Internal Process
  • Frequency Transformation
  • Fixed Distance